Method of Supporting Signal Transmission and Reception Using at Least Two Radio Access Technologies and Apparatus Therefor

1. A method of supporting signal transmission and reception using two or more radio access technologies (RATs) by a user equipment, comprising: receiving a setup message indicating access to a second base station of a second communication network supporting a second RAT, from a first base station of a first communication network supporting a first RAT; and searching the second base station satisfying a predetermined condition; wherein the predetermined condition includes: measured signal strength of the second base station is greater than measured signal strength of the first base station, or measured signal strength of the second base station is greater than a predetermined threshold, transmitting, to the first base station, a request message requesting access to the second base station of the second communication network, attempting to access the second base station, wherein if the access to the second base station is successfully performed, data on a specific traffic type is transmitted and received via the second base station, and data other than the specific traffic type is transmitted and received via the first base station.

2. The method of claim 1 , wherein the setup message comprises flow information indicating the specific traffic type, which is to be transmitted and received via the second base station.

3. The method of claim 1 , wherein the setup message comprises action time information indicating a time of communicating with the second base station and wherein the user equipment begins to transceive data with the second base station on a time indicated by the action time information.

4. The method of claim 1 , further comprising transmitting a completion message for reporting whether the access to the second base station is successful, to the first base station.

5. The method of claim 4 , wherein the completion message is transmitted only when the user equipment successfully accesses the second base station.

6. The method of claim 4 , wherein the completion message comprises a status value indicating whether the access to the second base station is successful.

7. The method of claim 4 , wherein the completion message comprises an address value assigned to the user equipment by the second base station.

8. The method of claim 4 , if the access to the second base station fails, further comprising re-receiving the setup message indicating an access to a new second base station from the first base station.

9. The method of claim 1 , wherein the setup message further comprises unit information indicating a unit of data to be switched to the second base station.

10. A method of supporting signal transmission and reception using two or more radio access technologies (RATs), which is supported by a first base station of a first communication network supporting a first RAT, comprising: transmitting a setup message indicating access to a second base station of a second communication network supporting a second RAT, to a user equipment supporting the two or more RATs; and receiving a completion message for reporting whether the access to the second base station is successful, from the user equipment, wherein if the user equipment successfully accesses to the second base station, transmitting data on a specific traffic type among data to be transmitted to the user equipment, to the second base station and transmitting data other than the specific traffic type directly to the user equipment, wherein when the user equipment fails to access the second base station, retransmitting the setup message indicating access to a new second base station, to the user equipment.

11. The method of claim 10 , wherein the setup message comprises flow information indicating the specific traffic type, which is to be transmitted and received via the second base station.

12. The method of claim 10 , wherein the setup message comprises action time information indicating a time of communication between the user equipment and the second base station and wherein the first base station redirects the data on the specific traffic type to the second base station on a time indicated by the action time information.

13. The method of claim 10 , wherein if the completion message is not received until a timer, which is started after the setup message is transmitted, expires, the first base station determines that access establishment between the user equipment and the second base station fails.

14. The method of claim 10 , wherein the completion message comprises a status value indicating whether the user equipment succeeds in accessing the second base station.

15. The method of claim 10 , wherein the completion message comprises an address value assigned to the user equipment by the second base station and wherein the first base station redirects the data on the specific traffic type based on the address value.

16. A user equipment supporting signal transmission and reception using two or more radio access technologies (RATs), comprising: a communication unit; and a processor configured to: control the communication unit to receive a setup message indicating access to a second base station of a second communication network supporting a second RAT, from a first base station of a first communication network supporting a first RAT, search the second base station satisfying a predetermined condition, wherein the predetermined condition includes: measured signal strength of the second base station is greater than measured signal strength of the first base station, or measured signal strength of the second base station is greater than a predetermined threshold, control the communication unit to transmit, to the first base station, a request message requesting access to the second base station of the second communication network, and control the communication unit to attempt to access the second base station, wherein if the access to the second base station is successfully performed, data on a specific traffic type is transmitted and received via the second base station and data other than the specific traffic type are transmitted and received via the first base station.

17. A base station of a first communication network supporting a first RAT, which supports signal transmission and reception using two or more radio access technologies (RATs), comprising: a communication unit; and a processor configured to control: the communication unit to transmit a setup message indicating access to a second base station of a second communication network supporting a second RAT to a user equipment supporting the two or more RATs, the communication unit to receive a completion message for reporting whether the access to the second base station is successful, from the user equipment, the communication unit to transmit data on a specific traffic type among data to be transmitted to the user equipment to the second base station and to transmit data other than the specific traffic type directly to the user equipment, when the user equipment successfully accesses to the second base station, and the communication unit to retransmit the setup message indicating access to a new second base station to the user equipment when the user equipment fails to access the second base station.